Linked Weak Reference Arrays A Hybrid Approach to Efficient Bulk - PowerPoint PPT Presentation

Linked Weak 
 Reference Arrays A Hybrid Approach to Efficient Bulk Finalization Andrés Valloud IWST 2015

Weak arrays ivars

Weak arrays ivars

Weak arrays mourn ivars 0

Ephemerons key

Ephemerons key

Ephemerons mourn key

GemStone/S Image GS Client Server

GemStone/S Image Ephemerons Server

GemStone/S Image Weak arrays Server

Observation overhead Ephemerons Weak arrays Evaluation Space required weak arrays at least one extra per client negligible much more object header object compact one extra weak arrays VM cost per finalization negligible much more client object queue slot efficient in bulk Finalization ephemerons weak arrays scanning for cost per client finalized only as induce linear tombstones object needed search

No scanning, deployed Begin interaction End interaction

No scanning, deployed Begin interaction 0 End interaction

No scanning, deployed Begin interaction S T R O N G C O P Y H E N C E N O T O M B S T O N E S End interaction

No scanning, deployed Begin interaction O R I G I N A L L Y W E A K isWeakContainer: false S T R O N G A T T H I S T I M E isWeakContainer: true W E A K O N C E A G A I N End interaction

No scanning, proposed Begin mourning 0 0 0 WeakArray>>mourn 1 to: self size do: [:eachIndex | (self at: eachIndex) == 0 ifTrue: [self mournAt: eachIndex] ] End mourning

No scanning, proposed Begin mourning 6 12 15 0 LinkedWeakArray End mourning

No scanning, proposed Begin mourning 6 12 15 0 LinkedWeakArray>>mourn | nextIndex | nextIndex := self firstTombstoneIndex. "6" [nextIndex == 0] whileFalse: [ self mournAt: nextIndex. nextIndex := self at: nextIndex "12, 15, 0" ] End mourning

No scanning, proposed Begin GC O R I G I N A L L Y W E A K VM queues for finalization setWeakContainer(false); S T R O N G A T T H I S T I M E LinkedWeakArray>>mourn isWeakContainer: true W E A K O N C E A G A I N End mourning

Mourning performance I 11.0 10.4 9.7 9.1 8.4 7.8 7.1 6.5 Quotient 5.8 5.2 4.5 3.9 3.2 2.6 1.9 1.3 0.6 0.0 1 2 3 5 7 10 Tombstoning rates

2^20 2^14 Tombstoning 
 rates 2^8 Linked weak 
 2^4 array sizes

Questions